Ship propeller

ABSTRACT

A ship propeller includes a hub having an outer periphery, a first blade set including a plurality of first blades each having a span-chord ratio substantially in a range of 3 to 8 and a second blade set including a plurality of second blades each having a span-chord ratio substantially in a range of 3 to 8. The first blade set and the second blade set are situated in different planes of rotation and working at the same rotation direction and the same rotation speed. Furthermore, the distance between the first blade set and the second blade set is 30 percent less than the mean blade radius. Specifically, the ship propeller has a total expanded area ratio substantially no less than 0.7.

FIELD OF THE INVENTION

The present invention relates to a ship propeller and, in particular, to a ship propeller for further improving propulsion efficiency of the ship.

BACKGROUND OF THE INVENTION

FIG. 1A and FIG. 1B show a conventional ship propeller 1, which includes a central hub 10 and a plurality of blades 13 around the hub. Traditionally, in order to achieve reasonable propulsion efficiency, the ship propeller 1 usually has a large expanded area ratio. Because the ship propeller 1 usually works in a limited space, the span length of each blade 13 is therefore limited. Under this limitation, to meet the demand of large expanded area ratio in a single plane of rotation, each blade 13 thus has a small span-chord ratio, wherein the span-chord ratio is defined as:

$\frac{\left( {R - r_{h}} \right)}{C_{m}}$

where R is the blade radius, r_(h) is the hub radius and C_(m) is the mean chord length, wherein the mean chord length is defined as:

$C_{m} = \frac{A_{b}}{\left( {R - r_{h}} \right)}$

where A_(b) is the blade area.

As natural resources become rarer and rarer, how to save energy is gradually becoming a very important issue. Accordingly, how to make a propulsion device work with higher efficiency is always pursued.

One of the attempts is the contra-rotating propeller. However, one drawback of contra-rotating propeller is that it has more complicated structure causing difficulties in fabrication and control. Therefore, there is a need to improve propulsion efficiency of a ship propeller in order to reduce energy consumption and running cost in a prerequisite of not increasing the fabrication complexity.

SUMMARY OF THE INVENTION

An object of this invention is to provide an energy-saving ship propeller for further improving propulsion efficiency so as to reduce energy consumption to reach the goal of saving energy and reducing the running cost in a prerequisite of not increasing the fabrication complexity.

To solve the foregoing problem, the ship propeller of the present invention includes: a hub having an outer periphery; a first blade set including a plurality of first blades, wherein each first blade has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub; and a second blade set including a plurality of second blades, wherein each second blade has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub. The first blade set and the second blade set are situated in different planes of rotation and working at the same rotation direction and the same rotation speed; and the distance between the first blade set and the second blade set is 30 percent less than the mean blade radius. Specifically, the ship propeller has a total expanded area ratio substantially no less than 0.7, and the cross-section of each first blade and the cross-section of each second blade are streamlined foil shape respectively. The plurality of second blades can be disposed without overlapping the plurality of first blades or alternatively disposed at least partially overlapping the plurality of first blades from the rotation axis view angle. The plurality of first blades and the plurality of second blades are evenly distributed around the outer periphery of the hub respectively.

The detailed technology and above preferred embodiments implemented for the present invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the accompanying advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein:

FIG. 1A is a front view of a conventional ship propeller.

FIG. 1B is a perspective view of the conventional ship propeller shown in FIG. 1A.

FIG. 2A is a perspective view of the ship propeller according to one embodiment of the present invention.

FIG. 2B is a side view of the ship propeller shown in FIG. 2A.

FIG. 2C is a front view of the ship propeller shown in FIG. 2A.

FIG. 3A is a front view of the ship propeller according to another embodiment of the present invention.

FIG. 3B is a front view of the ship propeller according to yet another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the cross-section of each of the blades of the ship propeller according to one embodiment of the present invention.

FIG. 5A illustrates a blade with a straight planform.

FIG. 5B illustrates a blade which is forwardly skewed.

FIG. 5C illustrates a blade which is backwardly skewed.

FIG. 5D illustrates a blade which is backwardly skewed in the region adjacent to the root portion and forwardly skewed in the region adjacent to the tip portion.

FIG. 5E illustrates a blade which is forwardly skewed in the region adjacent to the root portion and backwardly skewed in the region adjacent to the tip portion.

FIG. 6 is a diagram illustrating experimental data of a ship propeller according to the present invention and a conventional ship propeller.

DETAILED DESCRIPTION OF THE INVENTION

The detailed explanation of the present invention is described as following. The described preferred embodiments are presented for purposes of illustrations and descriptions, and they are not intended to limit the scope of the present invention.

The present invention discloses a ship propeller having a total expanded area ratio substantially no less than 0.7, in which the total expanded area ratio is the ratio of total blade area of the ship propeller divided by the propeller disc area. The ship propeller includes a hub having an outer periphery and a plurality of blade sets. Each of the plurality of blade sets includes a plurality of blades each having a span-chord ratio substantially in a range of 3 to 8 and projecting outward from the outer periphery of the hub. Moreover, the blade radius of each blade set can be identical or varied from one to another. In addition, the plurality of blade sets are situated in different planes of rotation and working at the same rotation direction and the same rotation speed, and the distance between two adjacent blade sets is 30 percent less than the mean blade radius. The mean blade radius for a number of blade sets is defined as:

$\frac{\left( {{R\; 1} + {R\; 2} + \ldots + {Rn}} \right)}{n}$

where n is the number of blade sets and R1 to Rn are the blade radii of the blade sets respectively.

In one preferred embodiment as shown in FIG. 2A, FIG. 2B and FIG. 2C, the ship propeller 2 includes a hub 20 having an outer periphery 201 and two blade sets which are the first blade set and the second blade set. The first blade set includes a plurality of first blades 231 each having a span-chord ratio substantially in a range of 3 to 8 and projecting outward from the outer periphery 201 of the hub 20. The second blade set includes a plurality of second blades 233 each having a span-chord ratio substantially in a range of 3 to 8 and projecting outward from the outer periphery 201 of the hub 20. Moreover, as shown in FIG. 2C, each first blade 231 has a first blade radius R1 and each second blade 233 has a second blade radius R2. In this embodiment, R1 is equal to R2. However, R1 can be greater or less than R2 in other embodiments and then the mean blade radius is equal to (R1+R2)/2. Furthermore, in this embodiment, the blade area of each first blade 231 is equal to the blade area of each second blade 233. However, the blade area of each first blade 231 can be greater or less than the blade area of each second blade 233 in other embodiments. In addition, the first blade set and the second blade set are situated in different planes of rotation and working at the same rotation direction and the same rotation speed, and the distance between the first blade set and the second blade set is 30 percent less than the mean blade radius. Specifically, the ship propeller 2 has a total expanded area ratio substantially no less than 0.7, wherein the total expanded area ratio is the ratio of total blade area of the ship propeller divided by the propeller disc area, which is defined as:

A _(d=π·(R) _(g))²

where A_(d) is the propeller disc area, it is circumference ratio and R_(g) is the greater one of R1 and R2.

In general, the total expanded area ratio of the ship propeller 2 is usually less than 1.

In this preferred embodiment, as shown in FIG. 2C, the plurality of second blades 233 are disposed without overlapping the plurality of first blades 231 from rotation axis view angle, and the plurality of first blades 231 and the plurality of second blades 233 are evenly distributed around the outer periphery 201 of the hub 20 respectively.

However, the plurality of second blades can also be disposed at least partially overlapping the plurality of first blades from rotation axis view angle in other embodiments. For example, as shown in FIG. 3A, the plurality of second blades (not shown) are disposed overlapping the plurality of first blades 231 a; as shown in FIG. 3B, the plurality of second blades 233 b are disposed partially overlapping the plurality of first blades 231 b.

FIG. 4 is a cross-sectional view showing the cross-section of each of the blades of the ship propeller 2. As shown in FIG. 4, the cross-section of each of the blades, the first blades 231 or the second blades 233, is made streamlined foil shape, so that the thrust can be generated with the least resistance when the ship propeller 2 is in working condition.

FIGS. 5A-5E illustrate several blade designs according to different aspects of the present invention. The blade design of the first blades 231 can be the same as or different from that of the second blades 233. In FIG. 5A, the first blades 231 are “unskewed”: each first blade 231 has a straight planform in which a radial center line of the first blade 231 is straight and the blade chords perpendicular to the radial center line are uniformly distributed about the line. In FIG. 5B, each first blade 231 is forwardly skewed: the blade center line curves in the rotation direction D of the ship propeller 2. In FIG. 5C, each first blade 231 is backwardly skewed: the blade center line curves away from the rotation direction D of the ship propeller 2. In FIG. 5D, each first blade 231 is backwardly skewed in the region adjacent to the root portion 2311 and forwardly skewed in the region adjacent to the tip portion 2313. In FIG. 5E, each first blade 231 is forwardly skewed in the region adjacent to the root portion 2311 and backwardly skewed in the region adjacent to the tip portion 2313.

Similarly, in FIG. 5A, the second blades 233 are “unskewed”: each second blade 233 has a straight planform in which a radial center line of the second blade 233 is straight and the blade chords perpendicular to the radial center line are uniformly distributed about the line. In FIG. 5B, each second blade 233 is forwardly skewed: the blade center line curves in the rotation direction D of the ship propeller 2. In FIG. 5C, each second blade 233 is backwardly skewed: the blade center line curves away from the rotation direction D of the ship propeller 2. In FIG. 5D, each second blade 233 is backwardly skewed in the region adjacent to the root portion 2331 and forwardly skewed in the region adjacent to the tip portion 2333. In FIG. 5E, each second blade 233 is forwardly skewed in the region adjacent to the root portion 2331 and backwardly skewed in the region adjacent to the tip portion 2333.

The effect of the present invention has been verified in experiments and numerical analysis, and the results of which are shown in FIG. 6, in which the present invention is compared with a conventional design therein. As shown in FIG. 6, the present invention attains higher propulsion efficiency. Especially, at high advance coefficient J, propulsion efficiency is significantly improved. Accordingly, the ship propeller according to the present invention achieves the object of reducing energy consumption to reach the goal of saving energy and reduce the running cost in a prerequisite of not increasing the fabrication complexity.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. A ship propeller, comprising: a hub having an outer periphery; and a plurality of blade sets, wherein each of the plurality of blade sets comprises a plurality of blades, wherein each blade has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub, wherein the plurality of blade sets are situated in different planes of rotation and working at the same rotation direction and the same rotation speed, wherein the ship propeller has a total expanded area ratio substantially no less than 0.7.
 2. A ship propeller according to claim 1, wherein the distance between two adjacent blade sets is 30 percent less than the mean blade radius.
 3. A ship propeller, comprising: a hub having an outer periphery; a first blade set comprising a first plurality of blades, wherein each of the first plurality of blades has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub; and a second blade set comprising a second plurality of blades, wherein each of the second plurality of blades has a span-chord ratio substantially in a range of 3 to 8 and projects outward from the outer periphery of the hub, wherein the first blade set and the second blade set are situated in different planes of rotation and working at the same rotation direction and the same rotation speed, wherein the ship propeller has a total expanded area ratio substantially no less than 0.7.
 4. A ship propeller according to claim 3, wherein the distance between the first blade set and the second blade set is 30 percent less than the mean blade radius.
 5. A ship propeller according to claim 3, wherein the cross-section of each of the first plurality of blades and the cross-section of each of the second plurality of blades are streamlined foil shape respectively.
 6. A ship propeller according to claim 3, wherein the second plurality of blades are disposed without overlapping the first plurality of blades from rotation axis view angle.
 7. A ship propeller according to claim 3, wherein the second plurality of blades are disposed at least partially overlapping the first plurality of blades from rotation axis view angle.
 8. A ship propeller according to claim 3, wherein the first plurality of blades and the second plurality of blades are evenly distributed around the outer periphery of the hub respectively.
 9. A ship propeller according to claim 3, wherein each of the first plurality of blades is forwardly skewed.
 10. A ship propeller according to claim 3, wherein each of the first plurality of blades is backwardly skewed.
 11. A ship propeller according to claim 3, wherein each of the first plurality of blades is backwardly skewed in the region adjacent to the root portion and forwardly skewed in the region adjacent to the tip portion.
 12. A ship propeller according to claim 3, wherein each of the first plurality of blades is forwardly skewed in the region adjacent to the root portion and backwardly skewed in the region adjacent to the tip portion.
 13. A ship propeller according to claim 3, wherein each of the second plurality of blades is forwardly skewed.
 14. A ship propeller according to claim 3, wherein each of the second plurality of blades is backwardly skewed.
 15. A ship propeller according to claim 3, wherein each of the second plurality of blades is backwardly skewed in the region adjacent to the root portion and forwardly skewed in the region adjacent to the tip portion.
 16. A ship propeller according to claim 3, wherein each of the second plurality of blades is forwardly skewed in the region adjacent to the root portion and backwardly skewed in the region adjacent to the tip portion. 